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Boiler Vapor vs. Liquid Temperature

edited January 2017 in General
This discussion was created from comments split from: My Rig.

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  • TS the boiler temp that is important is the temp of the gas in the boiler head.

  • I use liquid temp for a lot of things things.

  • That's a good position for a level switch to prevent dry fire though

  • edited December 2016

    @Tombstone I think @rossco is trying to say that vapour temp is the important factor as the boiling point of the liquid in the boiler will change depending on the amount of alcohol in it.

    @zymurgybob covers it well on this link: Zymurgy Bob's Distillation Facts - The Magic Boiling Myth

    Sure you can use the liquid temp, but not as a source for control (eg if using a PID) - it needs to be used in conjunction with a lookup table or graph (as per the link) to provide useful information IMHO.

    @jacksonbrown, can you please detail what you use the liquid temp for?

  • edited December 2016

    @crozdog said: the boiling point of the liquid in the boiler will change depending on the amount of alcohol in it.

    That's exactly what I use it for. The PID unit in my control box has a few alarms on it. (The power is set manually most of the time)

    One alarm is set to go off a few degrees before the boiling point ( usually it stays set to 85°C)
    That way a get a heads up that it's about to flow.

    The other alarm is set to go off when the boiler hits 99.8°C, that way I get a consistent cut off for feints collection.
    It basically tells me to shut it off as there's bugger left to collect.

  • That's pretty much what I do, with very slightly different numbers.

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

  • Vapor numbers are slightly different but the same reasoning. Guide for cuts, most important temp measurement.

  • I use vapour for cuts, well through an electric parrot.
    Hearts with the pot are usually between 74% and 65%. That might be a touch high but my column is packed with copper which bumps it up a bit.

  • I don't use it the temperature gauge was going to but I'm happy doing the old fashion way

  • edited December 2016

    Jackson I have an eparrot as well, cheers bloke.

    Sorry I should have been less cryptic.

    The vapor coming off the wash will tell the fractions in advance of any reading in the column. I do a few heads cuts in jars then switch to a large stainless vessel for the hearts, switch back to jars when the headspace vapor temp gets to 95degC tails will show up at around 96degC. At that point it is possible to take action on the RC to prevent the tails exiting the column into the collection jars.

    I learned from my Manu de Hanoi LM/VM, which has the therm halfway up.

  • @zymurgybob . I have just started to use the graph and understand the boiling temperature or a wash principal but having a little trouble with the logic on the red line ie vapor concentration. I would read that as for example a 40% wash will boil at say 83.5 c and a vapor concentration of say 95.6 % And a 20% wash will boil at 88.5 c and a vapor concentration of 98 % . A most useful graph.

    So therefore a lower strength solution will boil at a higher temp and have a more concentrated % output . Could you point me in the right direction to understand this and the ramifications in distilling.

  • OK pen into gear before brain. They are two separate plots on the same page. Easy

  • Yes they are separate, but they can be related to each other with along horizontal (same temp) or vertical (same %) lines. I don't have it in front of me to get exact numbers, but if you find your boiling point on the blue line, you can, as you said, follow the vertical line through that point down to % ABV in the wash. If you follow the horizontal line to the right from that point to the red line, you'll find the %ABV in the vapor coming off at that temp and wash %ABV.

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

  • Just need to say, I love my dragon!

    In goes 35% low wines, 2.8kW power, 13C cooling water.

    Out comes 89% @ 1.1 gal/yr using 3 pro plates

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